Visiting Vet: Veterinary marijuana

Using drugs on animals without sufficient scientific data can have unexpected and unwelcome consequences. –Courtesy iStock

Marijuana has been on my mind lately. I’m going to Jamaica soon with three teenage girls. (OK, one is technically in her 20s, but just barely.) Although marijuana is officially illegal there, we’ve heard that people openly sell ganja on the beach. I want to make sure these young women are prepared. Of course, it’s not just in Jamaica that marijuana is a hot topic. Over the past few weeks I have had the following conversations: My optometrist and I discussed patients who think marijuana cures just about everything, especially glaucoma; an insomniac friend tried an edible marijuana product as a sleep aid and, unprepared for the potency of modern products, had a distressingly disoriented evening, and I had an inquiry from a client who wondered if marijuana might reduce the size of a tumor on her cat’s leg.

With all the media talk about marijuana, and with changing state laws, cannabis is gaining acceptance for human medicinal use. Naturally, pet owners are interested in the veterinary possibilities. But when someone asks me about prescribing medical marijuana, I am faced with three major concerns — complicated legal status, lack of solid evidence-based information about veterinary medical use, and high risk in animals of adverse side effects and toxicity.

Marijuana is designated as a Schedule I controlled substance (defined by the DEA as drugs, substances, or chemicals with no currently accepted medical use and a high potential for abuse). Schedule I drugs include heroin, LSD, and ecstasy. By federal law, marijuana is illegal except in the most highly regulated circumstances, yet more than half of U.S. states have enacted legislation in direct opposition to this, permitting medicinal marijuana use in humans. Some states have also passed laws allowing recreational use, and in reality, marijuana is one of the most commonly used “illegal” drugs in the country.

Veterinarians are caught in the crossfire between state and federal law. We need our DEA licenses to practice medicine and prescribe medications. Prescribing medical marijuana could risk our licenses and our livelihoods.

In response to a recent uptick in interest in veterinary marijuana, the American Veterinary Medical Association (AVMA) Council on Biologic and Therapeutic Agents issued a publication in January 2018 titled “Cannabis: What Veterinarians Need to Know.” The AVMA reiterates that marijuana and its derivatives are illegal and not approved by the FDA for any medical use. It is illegal for veterinarians in ANY state to prescribe or recommend marijuana as a treatment. Acknowledging our conundrum, the paper states, “Marijuana and its derivatives including CBD are federally illegal, even though more than half of the states have legalized marijuana for human medical use. There are NO FDA-approved marijuana or hemp products for use in animals, and thus the legality of veterinarians recommending any unapproved products can be confusing.”

If legality weren’t an issue, would we prescribe marijuana? First let’s clarify some terms, and the difference between marijuana and hemp. Marijuana is a pharmaceutically diverse herb, Cannabis sativa, that may contain over 400 different compounds in widely varying concentrations in the flowers, resin, and leaves. The most widely studied compounds are cannabinoids, including tetrahydrocannabinol (THC), and cannabidiol (CBD). It’s THC that causes the “high.” Marijuana has been bred for high THC concentrations, and used for 5,000 years for recreational, religious, and medical purposes. It was made illegal in the U.S. in the 1930s.

Although technically a kind of cannabis plant, hemp is different. It looks different, has different uses, and contains only trace amounts of cannabinoids, primarily CBD. Historically, hemp has been used for textiles, foods, papers, body care products, detergents, plastics, and building materials.

The law has often lumped hemp and marijuana together, but in 2014 a change in the law permitted limited growing of hemp. Distinguishing hemp from marijuana helps with understanding both the legality and composition of commercially available CBD and hemp products. CBD products truly derived from hemp are unlikely to contain significant amounts of cannabinoids. There is no regulation or oversight of these products to verify CBD concentrations claimed on the labels. They are probably harmless, but in my opinion unlikely to be helpful, other than the placebo effect on pet owners. CBD oil made from medical marijuana contains much higher levels, but can only be purchased by prescription in states where medical marijuana is legal, and, not to keep harping on this point, it is still illegal under federal law.

OK, you say. You get it. You understand about federal laws, but you can procure marijuana products easily, without any real risk. Should you try them on your pet? Marijuana and its derivatives have been touted to treat anxiety, pain, nausea, seizures, and psychosis, and reported to have antibacterial, anti-inflammatory, and antioxidant properties. I suspect they will eventually have a place in veterinary medicine. Just not yet. Most scientific research has been about human use, not animal use. Pets are not just little people. Different species react to drugs differently. You can give aspirin to dogs, but it can kill cats. Cats are not harmed by ingesting sugarless products sweetened with xylitol, but xylitol can cause potentially fatal hypoglycemia in dogs. Pharmacology is not a one-size-fits-all-species science. Using drugs on animals without sufficient scientific data can have unexpected and unwelcome consequences, as my insomniac friend experienced.

Which brings us to marijuana toxicity, cases of which have increased exponentially in recent years. Dogs stealing brownies off the kitchen counter don’t discriminate between regular and “special” brownies. Toxicity has also been reported in cats, who may be attracted to cannabis like catnip. Effects can last up to five days in dogs, though usually resolve within 24 hours. Symptoms may include excessively rapid or excessively slow heart rate, low blood pressure, incoordination, vomiting, altered behavior, drooling, weakness, hypothermia, and seizures. There is no antidote, just supportive care. For now, with the current state of scientific knowledge and legal confusion about marijuana, I encourage my clients not to experiment on their pets … and I’m sitting down with my teenagers tonight to talk about not experimenting in Jamaica.